The use of lasers in various medical procedures is becoming quite common. The type of device used to deliver the laser energy from the laser to the treatment site is primarily dependant upon the wavelength of light generated. For example, 1.06 micron radiation generated by a Nd:YAG laser is typically delivered by an optical fiber formed from a silica compound. In contrast, 10.6 micron radiation generated by a CO.sub.2 laser is typically delivered through an articulated arm assembly since presently existing optical fibers will not efficiently transmit such longer wavelength radiation.
The present invention is intended for use with an articulated arm. The arm consists of a number of hollow segments connected by rotatable joints. Mirrors are located in each of the joints to redirect the laser beam down the next segment of the arm. One end of the arm is connected to the output of the laser while the other end carries a delivery element.
The delivery element is selected based on the type of medical procedure which is to be performed. A common delivery element is an endoscope 10 which is illustrated in cross section in FIG. 1. The endoscope in FIG. 1 is of the type that might be used in a laparoscopy and is often referred to as a laparoscope.
As seen in FIG. 1, the laparoscope body will typically have a number of axially extending bores 12, 14, 16 and 18. The laser beam may be directed through bore 12. Bore 14 may be used for optical feedback so the surgeon can view the tissue site. The two smaller bores 16 and 18 can be used to deliver illumination via fiber optic bundles to the treatment site.
In the prior art, a coupler is used to join the end of the articulated arm to the entrance of the endoscope. In the present commercial environment, a number of medical device companies manufacture and sell endoscopes each of which have slightly different entrance end configurations. For each different endoscope design, there exists a coupler with a complimentary mating design.
While there exists a wide variety of prior art coupler designs, all of the existing designs have a few common features. For example, the coupler is typically provided with a conically shaped male mating end which is received in a conically shaped female mating configuration formed at the entrance of the endoscope. The mating conical configurations allow the two pieces to be adjusted when mounted. The alignment of the system relies heavily on the accuracy of the mating cones.
Unfortunately, the latter mounting approach has been less than satisfactory. More particularly, the prior approach required the doctor to adjust and test the alignment of the beam each time a new endoscope was attached. Since a new sterile endoscope is used for each new surgical procedure, the doctor must repeatedly adjust the alignment of the system. More significantly, even if the doctor is able to initially align the beam, the continuous movement of the articulated arm during the surgical procedure often results in the alignment being lost. If the alignment is lost, the percentage of the beam power transmitted down the endoscope is adversely affected. Moreover, misalignment of the components affects beam shape and size. Accordingly, it would be desirable to provide an improved coupler which could provide accurate and stable alignment of the mating components.
Another common feature of prior art couplers was the inclusion of a single, positive focusing lens. The lens was used to focus the beam entering the coupler from the articulated arm into the endoscope. The power of the lens was designed to bring the beam to a focus just beyond the distal end of the endoscope.
The latter design has been used quite successfully with endoscopes wherein the diameter of the bore was quite large. When the bore diameter is large, a high percentage of the beam can be injected down the endoscope. Recently, there has been a trend to develop endoscopes with smaller outer diameters and associated smaller axial bores. As can be appreciated, doctors prefer smaller diameter endoscopes because they are easier to handle and the associated incisions can be made smaller. There has also been a trend to develop endoscopes wherein the diameter of the bore used to transmit the laser beam is reduced while increasing the diameter of the bore of the viewing channel to improve visibility at the treatment site.
When the diameter of the axial bore for transmitting laser radiation is reduced for either of the above discussed reasons, problems have arisen with the coupling of the laser beam into the endoscope. FIG. 2 illustrates the problem. As can be seen, when the focal power of the lens 20 is selected to bring the focus of the beam 22 near the end 24 of the endoscope 26, the diameter D.sub.1 of the beam at the entrance 28 will be significantly larger than the diameter D.sub.2 of the endoscope bore. This disparity results in severe clipping of the beam at the entrance reducing the power injected into the endoscope.
A further complication arises as the articulated arm is moved during the procedure. As the arm moves, the level of clipping is varied and the delivered power continuously changes. In addition, the beam is distorted as it reflects off the bore. This distortion causes an irregular shape burn that constantly changes with arm movement. Accordingly, it would be desirable to provide an improved coupler which overcame these problems.
Accordingly, it is an object of the subject invention to provide a new and improved coupler for use with medical laser delivery systems.
It is another object of the subject invention to provide a coupler configured to improve the alignment with the endoscope.
It is a further object of the subject invention to provide a coupler having an axially projecting alignment tube, receivable within the bore of the endoscope for improving alignment.
It is still another object of the subject invention to provide a coupler having an improved focusing system.
It is still a further object of the subject invention to provide a coupler with a telescope focusing system for reducing the clipping of the beam entering the endoscope.